The present invention relates to a pressure equalizing vessel used for a hemodialysis concentrate and comprising a substantially cylindrical upright vessel at the lower end of which a concentrate inlet provided with a valve is arranged and the upper portion of which is equipped with a venting means, said vessel comprising a conduit arranged on the upper portion thereof for discharging concentrate to a hemodialysis device.
During hemodialysis the dialysis fluid is normally prepared by mixing dialysis concentrate with water.
There are two different methods for producing or preparing dialysis fluid:
In the first method mixing is carried out by means of a volumetric mixing method wherein water and concentrate are intermixed at a given predetermined volumetric ratio, e.g. a ratio of 1:34.
A second method for preparing dialysis fluid is the conductivity-controlled method wherein the ratio of the water and concentrate flow is adjusted such that a specific conductivity is obtained in the finished dialysis fluid.
The dialysis fluid is typically prepared from one or two concentrates and water. However, it is also possible to prepare the dialysis fluid from more than two concentrates and from water.
In practice, the dialysis concentrate is provided in two different ways. On the one hand, it is possible to provide the dialysis concentrate in the conventional way, i.e. in canisters, to suck it in, using a concentrate pump of the hemodialysis device, and to supply it to a mixing means in which the dialysis concentrate is mixed with prepared water. This kind of preparing dialysis fluid permits a certain flexibility when the composition of the dialysis fluid is chosen, but requires considerable efforts, as the canisters must be transported, provided and disposed of. Furthermore, it is always necessary to suitably connect the canisters to a concentrate suction conduit. This may result in malfunctions. The disposal of the empty canisters poses considerable problems because of the resultant waste as such and because of the relatively large volume of the empty canisters.
Central concentrate supply systems have therefore been developed wherein the concentrates are delivered under pressure from a central container to respective tapping or connecting points of the hemodialysis device.
The concentrate pumps which are normally used in hemodialysis devices are so constructed that their delivery rate depends on the input pressure. It is therefore necessary to equalize the normally varying pressure of a central concentrate supply system, so that the delivery rate of the mixing pump is not impaired by pressure variations. Pressure equalizing containers have therefore been designed which consist of a ventilable vessel and a level regulating system. For instance, float switches are used for actuating a concentrate inlet valve and/or a valve in an outlet conduit leading to the hemodialysis device.
The prior art discloses pressure equalizing containers which comprises a connection for a concentrate suction conduit at the side of the equalizing vessel or in the bottom thereof. However, the concentrate suction conduit may also be designed in the form of a suction tube which can be introduced into a concentrate canister, as is known from German patent application 37 34 880.